Mechanical computers, old instructional videos
If you haven’t seen this yet and you have a spare 40 minutes I really really recommend it.
Old instructional videos from the US Navy on the inner workings of the mechanical computers that used to be used to work out the correct firing positions for moving ships. The amount of variables taken account of is stunning, but mostly I just like the way the videos are all about explaining individual components rather than complicating details.
Ie, these are the mechanics for x*y multiplication and how they work, these are for x+y and how they work, etc.
